control they must provide no sensation of illness after ingestion. For this purpose, baits containing anticoagulants such as Warfarin were long used; they kill relatively slowly through internal bleeding, which is not associated with ingestion. More recently a highly potent toxin attacking the central nervous system, bromethalin, has been used. Again, with sub-lethal doses of this chemical, the animal cannot learn the association between the odour of the food and its toxicity, thereby preventing poison shyness from developing. Crows: Conditioned taste aversion has been used to control crow (Corvus brachyrhynchos) predation on eggs – a problem for bird sanctuaries and farmers with outdoor chickens. The researchers put a sickness-causing agent in several eggs, painted them green and then placed them where crows could eat them. After eating the tainted eggs, the crows avoided eating green eggs. The crows subsequently avoided eating green eggs whether they contained toxin or not. The crows also continued to eat unpainted and non-toxic chicken eggs. However, another study tested if carrion crow (Corvus corone) predation on little tern (Sterna albifrons) eggs could be decreased by conditioned taste aversion. The study failed to find an effect because the crows were able to distinguish treated eggs during handling, without consuming a significant amount of the illness-inducing compound. Quoll: In Australia, a critically endangered predator, the northern quoll (Dasyurus hallucatus) is threatened by the invasion of the highly toxic cane toad (Bufo marinus). After toad invasion, quoll populations have become extinct across Northern Australia. A conditioned aversion to live toads in juvenile northern quolls was successfully established by feeding them a dead toad containing a nausea-inducing chemical (thiabendazole). Multiple predators: When surrogate eggs of the sandhill crane (Grus canadensis) were laced with an illness-producing substance, egg predation decreased in a location which contained multiple potential predators. Coyotes: Poisoned baits of meat left where coyotes can find them have been used to discourage coyotes from attacking sheep. Here, bait shyness is transferred from the pieces of meat to an aversion for live sheep. Bait shyness may sometimes be location specific and not transferred to different localities. Livestock protection Taste aversions have been developed in wolves, coyotes, and other canids to protect livestock and vulnerable wildlife. In 1974, it was reported that coyotes (Canis latrans) learned to avoid hamburger after eating hamburger treated with lithium chloride and could transfer such a drug-induced aversion of LiCl-tainted sheep or rabbit (Sylvilagus sp.)